Wind Farms Warming Texas

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New research finds that wind farms actually warm up the surface
of the land underneath them during the night, a phenomena that
could put a damper on efforts to expand wind energy as a green
energy solution.

Researchers used satellite data from 2003 to 2011 to examine
surface temperatures across as wide swath of west Texas, which
has built four of the world's largest wind farms. The data showed
a direct correlation between night-time temperatures increases of
0.72 degrees C (1.3 degrees F) and the placement of the farms.

"Given the present installed capacity and the projected growth in
installation of wind farms across the world, I feel that wind
farms, if spatially large enough, might have noticeable impacts
on local to regional meteorology," Liming Zhou, associate
professor at the State University of New York, Albany and author
of the paper published April 29 in Nature Climate Change said in
an e-mail to Discovery News.

Analysts say wind power is a good complement to solar power,
because winds often blow more strongly at night while solar power
is only available during daytime hours. But Zhou and his
colleagues found that turbulence behind the wind turbine blades
stirs up a layer of cooler air that usually settles on the ground
at night, and mixes in warm air that is on top.

That layering effect is usually reversed during the daytime, with
warm air on the surface and cooler air higher up."The
year-to-year land surface temperature over wind farms shows a
persistent upward trend from 2003 to 2011, consistent with the
increasing number of operational wind turbines with time," Zhou
said.

FAA data shows that the number of wind turbines over the study
region has risen from 111 in 2003 to 2358 in 2011, according to
the study.The warming could hurt local farmers, who have already
suffered through a killer drought over the past few years. Texas
agriculture contributes $80 billion to the state's economy,
second only to petrochemicals, according to the Texas Department
of Agriculture.

West Texas is a dry area that uses irrigation to grow wheat,
cotton and other crops, as well as raise cattle. But increased
warming can play havoc with plant growth, as well as change local
rainfall patterns.

Texas wind farms produce more than 10,000 megawatts of
electricity, more than double the capacity of the nearest state,
Iowa, and enough to power three million average American homes,
according to the
American Wine Energy Association.

One solution could be to change the shape of the turbine blades,
according to John Dabiri, director of the Center for Bioinspired
Wind Energy at the California Institute of Technology who is an
expert on wind power design.

"Smaller turbines can avoid this problem," Dabiri said. "However,
this presents a tradeoff, because wind speed decreases as you
move closer to the ground; so the smaller turbines would
experience lower incoming wind speeds on average."

That means a smaller turbine makes less power.

Dabiri said Zhou's findings may mean taking a second look at the
trade-offs with renewable energy. "It shows that we need to think
carefully about the unintended environmental consequences of any
large-scale energy development," Dabiri said, "including green
technologies."

Zhou cautioned that his study used satellite data, which can have
errors from clouds, for example, rather than temperature readings
taken at the surface. He said he hopes to improve his dataset,
and look at wind farms in other parts of the world.